Investigation of Material Models for Laser Welds in Crash Applications using LS-DYNA

In general the body-in-white (BIW) consists of thin walled structures joined with adhesives, spot welds, laser welds etc. Due to the efficiency and reliability of laser welding, it is increasingly applied in automotive applications to join structures made of steel. The analysis of the behavior of all these joining technologies at crash is generally of great interest. Therefore a suitable model for spot welds has been already published by DaimlerChrysler AG at the LS-DYNA Forum 2005 [2]. Although there are a lot of similarities between laser welds and spot welds, new models and methods are required due to different weld properties and numerous possible laser weld geometries. Because the crash model of a BIW target structure consists of a relatively coarse mesh, a simplified model with reduced complexity is needed. Besides the modeling technique, the material model determines the quality and the efficiency of the modeled laser weld and BIW model. In this paper three different material models are investigated: a bi-linear elasto-plastic material (MAT100), a linear elastic visco-plastic material (MAT24) and a new linear elastic material with an anisotropic yield surface according to Hill, viscoplasticity and anisotropic damage according to Chaboche together with a failure criterion are compared. These material models are tested on standard substitute joint models with a single weld, where the weld has been modeled with a solid element.